The semiconductor fabrication industry requires materials and deposition technology adequate to deposit metals, metal mixtures and metal compound mixtures in thin layers, plugs, vias and patterns on semiconductor and insulating or dielectric substrates to make appropriate electrical devices for integrated circuits, memory devices and flat panel display devices.
Various techniques are known for depositing metals, metal compounds and their mixtures on appropriate electronic materials substrates, including; physical methods (sputtering, molecular beam epitaxy, evaporation and laser ablation), alloying, and chemical vapor deposition (plasma, photo or laser enhanced, low pressure and high temperature).
Various multiple metal oxides are known in the literature, including those recited in: "Advances in Processing of Ferroelectric Thin Films", L. M. Sheppard, Ceramic Bulletin, Vol. 71, No. 1, (1992), pp. 85-95; "Formation of Al.sub.2 O.sub.3 --Ta.sub.2 O.sub.5 Double-Oxide Thin Films by Low-Pressure MOCVD and Evaluation of Their Corrosion Resistances in Acid and Alkali Solutions", Hara, et. al., Journal of the Electrochemical Society, 146 (2) (1999), pp. 510-516; "High Coercivity in Sm.sub.2 Fe.sub.17 N.sub.x Magnets", Schnitzke, et. al., Appl. Phys. Lett. 57 (26) Dec. 24, 1990, pp. 2853-2855; "Investigation of Ternary Transition-Metal Nitride Systems by Reactive Cosputtering", Van Dover, et. al., Chem. Mater. (1993), Vol. 5, pp. 32-35; "Reactively Sputtered Ti--Si--N Films II. Diffusion Barriers for Al and Cu Metallizations on Si", Sun, et. al., J. Appl. Phys., 81 (2) Jan. 15, 1997, pp. 664-671; "MOCVD Routes to Thin Metal Oxide Films for Superconducting Electronics", Schulz, et. al., Adv. Mater. (1994), 6 No. 10, pp. 719-730; "Compositional and Microstructural Characterization of RuO.sub.2 --TiO.sub.2 Catalysts Synthesized by the Sol-Gel Method", Guglielmi, et. al., J. Electrochem. Soc., Vol. 139, No. 6, June 1992, pp. 1665-1661; "Enhancement of the Dielectric Constant of Ta.sub.2 O.sub.5 Through Substitution with TiO.sub.2 ", Cava, et. al., Nature, Vol. 377, 21, September 1995, pp. 215-217; and U.S. Pat. No. 4,058,430, the latter of which also discloses the deposition process known as "atomic layer epitaxy".
Chemical vapor deposition (CVD) has gained favor in recent years due to its properties of providing uniform and conformal deposition and its ability to deposit an array of materials under highly controllable conditions. Typically, chemical vapor deposition can provide high deposition rates of high purity materials in a controlled fashion.
However, chemical vapor deposition has several drawbacks which make its implementation challenging. Not all desired chemicals are sufficiently volatile to make themselves amenable to chemical vapor deposition. Some chemicals are solids at storage or delivery conditions. Some chemicals are too volatile for adequate storage and delivery.
The situation for chemical vapor deposition is further complicated by the need to co-deposit several chemicals such as in multiple metal chemical vapor deposition, such as multiple metal oxide chemical vapor deposition. It is possible for metal precursors to react with one another or for at least one metal precursor for CVD to be too volatile or too involatile, i.e., a solid.
To overcome these disadvantages of CVD, the prior art has used solvents to dissolve solid metal precursors or blend liquid, particularly viscous liquid, metal precursors for CVD.
U.S. Pat. No. 5,204,314 discloses a foraminous device for flash vaporization of liquid mixtures or solvent mixtures of metal precursors for CVD.
U.S. Pat. No. 5,820,664 describes various solvent mixtures of mixed metal compound precursors, which are useful for CVD.
However, solvent systems for liquid delivery for CVD are problematic because compatible, volatile solvents must be chosen. Solvents decrease the amount of effective reagent that is delivered for a given flow and time period. More importantly, solvents introduce yet another reagent into the sensitive reaction zone where delicate semiconductor and electronic device fabrication is being performed. The adverse effects of such solvent presence must be considered. Finally, solvents represent an environmental and cost factor. The solvent or its degradation products must be recycled, captured or treated subsequent to utilization.
International Patent Application WO98/46617 describes metal precursors and processes for deposition of metals from mixed .beta.-diketonates. The application addresses liquid delivery of metal precursors for CVD and other depositions by direct liquid injection. Using mixed .beta.-diketonates enhances the liquid state of the precursors to facilitate delivery. Solvents are an option for the liquid mixtures.
Similar disclosures appeared in "New Liquid Precursors for Chemical Vapor Deposition", Gordon, et. al., Mater. Res. Soc. Symp. Proc., 495, (1998), pp. 63-68; and "Liquid Compounds for CVD of Alkaline Earth Metals", Gordon, et. al., MRS Meeting, Apr. 7, 1999, San Francisco, Calif.
The prior art attempts to provide appropriate liquid media for metal precursor delivery have required the use of selected solvents or mixed .beta.-diketonate ligands to assure liquid conditions for delivery. Solvents constitute problems of contamination and abatement. Mixed ligands constitute problems of inadvertent ligand exchange which can lead to non-liquid conditions. The .beta.-diketonate ligands frequently lead to solid metal compounds absent manipulation of the .beta.-diketonate substituents to avoid conditions leading to solid conditions, thus aggravating the consequences of inadvertant ligand exchange. The present invention overcomes these drawbacks by using a solventless, common ligand mixture of metals in a liquid state for deposition preferably by direct liquid injection to avoid solvent and ligand exchange drawbacks for consistent deposition performance.